Phosphorous-containing organopolysiloxane lubricant



United States Patent 3,479,290 PHOSPHOROUS-CONTAINING ORGANOPOLY-SILOXANE LUBRICANT Edgar D. Brown, In, Schenectady, N.Y., assignor togeneral Electric Company, a corporation of New ork No Drawing. FiledDec. 12, 1966, Ser. No. 600,757 Int. Cl. C10m 1/44, [/50 US. Cl.252-49.9 7 Claims ABSTRACT OF THE DISCLOSURE An organopolysiloxanelubricating composition comprising (A) an organopolysiloxane having theformula:

cum. f

SIiO snow); CH3 CH3 b and (B) from 1 to percent by weight, based on theweight of said organopolysiloxane, of tricresyl phosphate, where R is analkyl radical containing from 8 to 18 carbon atoms, inclusive, n has avalue of from 2 to 6, inclusive, a has an average value of at least 1, bhas an average value of at least about 2.9, the sum of a plus b is equalto from about 4 to 40, inclusive, and the ratio of a to the sum of aplus b is equal to from 0.1 to 0.4, inclusive.

The present invention is directed to a new class of organopolysiloxanelubricants in which extreme pressure lubricating characteristics areimparted by certain phosphorous compounds.

In my copending application Ser. No. 421,588, filed Dec. 28, 1964, nowUS. Patent No. 3,418,353 granted Dec. 24, 1968 and assigned to the sameassignee as the present invention, there is described a class oforganopolysiloxanes useful for many purposes, which comprisestriorganosilyl chain-stopped diorganopolysiloxanes in which each of thediorganosiloxane units contains a siliconbonded higher alkyl radical.Examination of these materials shows that they have very goodlubricating properties under moderate pressure conditions. However, whenthe pressure under which these compositions are to operate is increased,it is found that the fluids do not have as high a lubricatingcharacteristic as desired. This is particularly true with respect to thelubrication of stainless steel parts.

In my copending application Ser. No. 600,768 filed concurrently herewithand assigned to the same assignee as the present invention, there isdescribed a class of organopolysiloxane liquids of improved lubricatingcharacteristics which are trimethylsilyl chain-stopped copolymers ofmethylchloroalkylsiloxane units and methyl higher alkylsiloxane units.While these copolymers have improved lubricating characteristics, thelubricating characteristics are still not as good as desired,particularly under extreme pressure lubricating conditions. While thesecopolymer fluids of my aforementioned copending application Ser. No.600,768 have been useful in many applications, there have been manyengineering designs which would normally have made use of thecorrosion-resistance of stainless steel but which, because of theinability to lubricate satisfactorily stainless steel under extremepressure conditions, has required the use of other materials.

The present invention is based on my discovery of a lubricatingcomposition which contains both methylchloroalkylsiloxane units andmethyl higher alkylsiloxane units, and which also contain tricresylphosphate. This combination of components provides a lubricatingcomposition which has improved high temperature stainless steel extremepressure lubricating characteristics.

Patented Nov. 18, 1969 The compositions of the present inventioncomprise (A) an organopolysiloxane fluid having the average formula:

R Si(CH3)3 C 3 1: C 3 1:

where R is an alkyl radical containing at least 8 carbon atoms, e.g.,from 8 to 18 carbon atoms, 11 is equal to from 2 to 6, inclusive, a hasan average value of at least 1, b has an average value of at least 2.9,the sum of a plus b is equal to from about 4 to 40, inclusive, and theratio of a to the sum of a plus b is equal to from 0.1 to 0.4,inclusive, and (B) from 1 to 15 percent by weight, based on the weightof the polysiloxane, of tricresyl phosphate.

The fact that tricresyl phosphate will increase the stainless steellubricating characteristics of the compositions of Formula 1 iscompletely unexpected and unpredictable from the art, since the additionof tricresyl phosphate to a methyl higher alkyl polysiloxane fluid ofthe type described in my aforementioned copending application Ser. No.421,588, or the addition of tricresyl phosphate to a trimethylsilylchain-stopped methylchloroalkylpolysiloxane fluid fails to increase thelubricating characteristics of such fluids. On the other hand, theaddition of the tricresyl phosphate to the compositions of the presentinvention has a dramatic effect in increasing the lubricatingcharacteristics of the composition.

The organopolysiloxane fluids within the scope of Formula 1 can becopolymers in which the average molecule contains bothmethylchloroalkylsiloxane units and methyl higher alkylsiloxane units orcan be a blend of two fluids, one of which is a trimethylsilylchain-stopped methylchloroalkylsiloxane fluid having the formula:

c1 u Zn onmsio l orrmsio suoHm when n is as previously defined and c hasa value of from about 4 to 40, inclusive, and the other of which is atrimethylsilyl chain-stopped methyl higher alkylpolysiloxane having theformula:

where R is as previously defined and d has a value of from about 4 to40, inclusive.

The trimethylsilyl chain-stopped methylchloroalkylpolysiloxane fluids ofFormula 2 are formed by the relatively straightforward hydrolysis andcondensation of trimethylchlorosilane and amethylchloroalkyldichlorosilane having the formula:

(4) (CH (C1C H )SiCl Where n is as previously described. Generally, thishydrolysis and condensation is effected by mixing the stoichiometricamounts of the trimethylchlorosilane and the methyl higheralkyldichlorosilane, adding the resulting mixture to a stirred excess ofice water to eifect the hydrolysis and condensation, allowing thereaction mixture to separate into an upper silicone phase and a loweraqueous phase, separating the phases, washing with water to remove allacidic by-products, and drying the resulting product to form thepolysiloxane within the scope of Formula 2.

As is obvious from the definition of the organopolysiloxane of Formula2, the methylchloroalkyldichlorosilane of Formula 4 includes compoundsin which the chloroalkyl radical can vary from chloroethyl tochlorohexyl. While it is preferred that the chlorine atom of thechloroalkyl radical be attached to the omega-carbon atom of a normalalkyl radical, it is also possible for the chlorine atom to be attachedto any other carbon atom of the alkyl radical and it is also possiblefor the alkyl radical to be other than a normal alkyl radical. In anyevent, it is preferred that the chlorine atom be attached to a carbonatom other than the carbon atom attached to silicon. In the preferredembodiment of my invention, the chloroalkyl radical is the chloropropylradical.

The trimethylsilyl chain-stopped methyl higher alkylsiloxane of Formula3 is prepared from the corresponding trimethylsilyl chain-stopped methylhydrogen polysiloxane which has the formula:

(5) III (CH3)3S O[sIlO :Isnomn on, d

This fluid is well known in the art and is prepared by the hydrolysisand condensation of trimethylchlorosilane and methyl hydrogendichlorosilane in the proper proportions. The fluid within the scope ofFormula 3 is then prepared by the general method described in myaforementioned copending application Ser. No. 421,588, by the additionof a suitable alpha-olefin to the methyl hydrogen polysiloxane fluid ofFormula 5. In general, the preferred alpha-olefin is tetradecene-l, butany other alphaolefin having from about 8 to 18 carbon atoms can beemployed, for example, octene-l, decylene-l, dodecylene- 1,tetradecylene-l, hexadecylene-l, and octadecylene-l.

My aforementioned copending application Ser. No. 421,588 is incorporatedby reference into the present application for a disclosure of methods offorming the compositions within the scope of Formula 3. In general, thereaction involves one molecule of the alpha-olefin for eachsilicon-bonded hydrogen atom in the polysiloxane of Formula 5 and thisis the ratio of components employed in the reaction. However, sometimesit is advantageous to add the alpha-olefin in a to 20% molar excess. Thereaction is carried out in the presence of conventional SiH-olefinaddition catalysts, with the preferred type being the elemental platinumcatalysts of the type described in Patent 2,970,150-Bailey, as well asthe platinum compound catalysts described in Patents 2,823,- 218Speieret al.; 3,159,60lAshby; 3,159,662Ashby; and 3,220,972-Lamoreaux.

The amount of SiH-olefin addition catalyst employed in effectingreaction between the polysiloxane of Formula 5 and the alpha-olefin canvary within wide limits. Generally, the catalyst is employed in anamount suflicient to provide one mole of platinum per 1,000 moles ofalphaolefin to one mole of catalyst per million moles of alphaol efin.Generally, a mixture is formed of the hydrogencontaining polysiloxane ofFormula 5 and a portion of the alpha-olefin and the' catalyst is added,the temperature of the reaction mixture is increased until the rate oftemperature rise becomes greater than that supplied by the heatingelement, and thereafter the temperature is maintained by controlling therate of addition of the remaining alpha-olefin. Generally, the reactiontemperature is maintained at about to C. When an excess of thealpha-olefin is employed, it is removed from the reaction mixture bydistillation.

The organopolysiloxane fluids within the scope of Formula 1 which arecopolymers in which the average molecule contains both themethylchloroalkylsiloxane unit and the methyl higher alkylsiloxane unitare prepared by the process described in my aforementioned copendingapplication Ser. No. 600,768, which is incorporated by reference intothe present application for details of the technique for the preparationof such copolymers. In general, the procedure for preparing thecopolymers of Formula 1 is to first form a trimethylsilyl chain-stoppedcopolymer of methylchloroalkylsiloxane units and methyl hydrogensiloxane units having the formula:

ohm. f (OHmSiO siro worn CH3 3 CH3 b where a, b and n are as previouslydefined. This copolymer of Formula 6 is prepared by the cohydrolysis andco-condensation of a mixture of trimethylchlorosilane, methyl hydrogendichlorosilane, and a methylchloroalkyldichlorosilane within the scopeof Formula 4. The process for forming the composition of Formula 6 isconventional, with the appropriate chlorosilanes being mixed together inthe proper ratios, and added to an excess of ice water, with thesubsequent isolation of the product.

Following the procedure previously described for preparation of thetrimethylsilyl chain-stopped methyl higher alkylpolysiloxane of Formula3, the methyl hydrogencontaining polysiloxane of Formula 6 is reactedwith the appropriate alpha-olefin employing a platinum compound orelemental platinum catalyst to produce the composition within the scopeof Formula 1 which is a copolymer hav ing both the methyl higheralkylpolysiloxane unit and the methylchloropropylsiloxane unit presentin the same molecule.

When the composition of Formula 1 comprises a blend of a fluid ofFormula 2 and a fluid of Formula 3, the two fluids are merely mixedtogether with agitation, and the tricresyl phosphate is added in thedesired amount. The tricresyl phosphate is generally soluble in one orboth of the organopolysiloxane fluids in the blend, and the tricresylphosphate in the blend is merely stirred until the tricresyl phosphategoes into solution.

In addition to copolymeric organopolysiloxanes within the scope ofFormula 1 and blends of methylchloroalkylpolysiloxane fluids of Formula2 with methyl higher alkylpolysiloxanes of Formula 3 which result in anaverage blend composition within the scope of Formula 1, it should alsobe understood that within the contemplation Of the present invention areblends of copolymers within the scope of Formula 1 with eithermethylchloropropylpolysiloxanes within the scope of Formula 2 or methylhigher alkylpolysiloxanes within the scope of Formula 3, so long as theresulting composition has an average formula which falls withinFormula 1. Likewise, it is possible to employ blends of copolymers ofFormula 1 with both methylchloropropylpolysiloxanes of Formula 2 andmethyl higher alkylpolysiloxanes of Formula 3, so long as the resultingblend has the average composition of Formula 1.

The tricresyl phosphate employed in the practice of the presentinvention has the formula:

and, as is well known in the art, can comprise a number of isomers.Thus, the methyl groups in the cresyl radicals can be ortho, meta, orpara to the oxygen atom in the radical. In general, commercial tricresylphosphate is a random mixture of the various tricresyl phosphate isomersand this random mixture was employed in the practice of the presentinvention. However, it should be understood that within the scope of thepresent invention are single isomers of tricresyl phosphate, in additionto the random mixture of such isomers.

The copolymeric siloxanes within the scope of Formula 1 are goodsolvents for tricresyl phosphate, for the methylchloroalkylpolysiloxaneof Formula 2, and for the'methyl higher alkylpolysiloxane of Formula 3.Therefore, in the preferred embodiment of my invention, the compositionwithin the scope of Formula 1 includes a copolymer within the scope ofFormula 1 even though the composition can also contain the polysiloxaneof Formula 2 or of For mula 3. In preparing the compositions of thepresent invention which contain copolymers within the scope of Formula1, the tricresyl phosphate is merely added to the other components ofthe composition in the appropriate ratio and a uniform solution isobtained.

Because the methylchloroalkylpolysiloxane of Formula 2 is not completelymiscible with the methyl higher alkylpoysiloxane of Formula 3, when thecomposition of the present invention is a blend of these twopolysiloxanes with the tricresyl phosphate added, the resulting materialis a two-phase mixture and conventional precautions are employed toinsure that the compositions are uniformly and constantly mixed.Therefore, these compositions are most often employed in dynamiclubrication environments.

In order to evaluate the lubricating characteristics of the compositionsof the present invention, they were subjected to the conventional ShellFour-Ball Wear test in which three rigidly clamped /2" 302 stainlesssteel balls in a metal cup are covered with the lubricant underevaluation. A fourth rotating 302 stainless steel ball of the samediameter is then pressed into contact with the three stationary balls byan adjustable loading arm. The fourth ball rotates at a speed of 600r.p.m. at ambient temperature for one hour. The contact points betweenthe rotatable ball and the three stationary balls grow to circular scarsas wear progresses. The average diameter of these scars in millimeters,after the one hour run, is taken as the measure of wear. The better thelubricity of the fluid, the lower is the wear scar.

The following examples are illustrative of the practice of my inventionand are not intended for purposes of limitation. All parts are byweight.

EXAMPLE 1 A methylchloropropylpolysiloxane fluid within the scope ofFormula 2 was prepared by mixing g. (0.92 mole) trimethylchlorosilanewith 197 g. (1.0 mole) methy1chloropropyldichlorosilane and the mixturewas added to 600 g. of water and stirred for one hour. At the end ofthis time, the two layers were separated and the uppermethylpolysiloxane layer was washed with water three times until neutraland then dried over sodium sulfate to produce a polysiloxane within thescope of Formula 2 where n is 3, and c has a value of about 25.Following the procedure of my copending application Ser. No. 421,588, amethyltetradecylpolysiloxane fluid was prepared by slowly adding 196 g.of tetradecene-1 to 63 g. of a trimethylsilyl chainstopped methylhydrogen polysiloxane within the scope of Formula 5, where c was equalto 40. This resulted in a trimethylsilyl chain-stoppedmethyltetradecylpolysiloxane within the scope of Formula 3 in which R istetradecyl and d is 40. A mixture was prepared of 92 parts of themethyltetradecylpolysiloxane and 8 parts of themethylchloropropylpolysiloxane. This blend was within the scope ofFormula 1 when n was equal to 3, R is equal to tetradecyl, and theaverage value of a was 6 and the average value of b was 32. To 100 partsof this blend was added 5 parts of tricresyl phosphate and the wear scarwas determined with type 302 stainless steel balls at 600 r.p.m., atambient temperature, and under loads of 10 kg. and 20 kg: The wear scarat 10 kg. was 0.36 mm. and at 20 kg. was 0.43 mm. In comparison to this,the wear scar of a mixture of 100 parts of themethyltetradecylpolysiloxane and 8 parts of themethylchloropropylpolysiloxane at 10 kg. was 2.4 mm. In contrast also,the wear scar of a solution of 5 parts of tricresyl phosphate in 100parts of the methyltetradecylpolysiloxane fluid was 2.6 mm. Also incontrast to this, the wear scar of a solution of 5 parts of tricresylphosphate in 100 parts of the methylchloropropylpolysiloxane fluid was2.5 mm. With the methyltetradecylpolysiloxane fluid, destructive failureoccurred after minutes and the test could not be run for a full hour.Thus, the data of Example 1 show that with a polysiloxane fluidcontaining both the methyltetradecylsiloxane groups andmethylchloropropyl-siloxane groups and the tricresyl phosphate,satisfactory lubrication occurred under loads 6 of 10 kg. and 20 kg. Incontrast to this, when any of the three components was omitted from thereaction mixture, the wear scar increased drastically.

EXAMPLE 2 Following the procedure of my aforementioned copendingapplication Ser. No. 600,768, a trimethylsilyl chainstopped copolymer ofmethylchloropropylsiloxane units and methyl hydrogen polysiloxane unitswithin the scope of Formula 6, when n is 3, a is 8, and b is 32 (-20-copolymer), was prepared by the hydrolysis and condensation of a mixtureof trimethylchlorosilane, methylchloropropyldichlorosilane, and methylhydrogen dich1orosilane. This polymer was then reacted withtetradecene-l following the procedure of the same application, toproduce a copolymer within the scope of Formula 1 in which n is 3, a is8, b is 32, and R is tetradecyl. To parts of this fluid was added 5parts of tricresyl phosphate and evaluation of this material in thelubrication of type 302 stainless steel showed a wear scar at 10 kgs. of0.37 mm.

EXAMPLE 3 A mixture was prepared from 29.7 parts of themethyltetradecylpolysiloxane described in Example 1, and 100 parts ofthe copolymer containing methyltetradecylsiloxane units andmethylchloropropylsiloxane units of Exam ple 2, to produce apolysiloxane blend within the scope of Formula 1 corresponding to theaverage composition in which n is 3, R is tetradecyl, a is 6 and b is32, and then 5 parts tricresyl phosphate was added. Evaluation of thismaterial in the Shell Four Ball Wear tester gave identical results tothe results obtained in Example 1. The wear scar at 10 kg. was 0.36 mm.and the wear scar at 20 kg. was 0.43 mm.

EXAMPLE 4 A mixture was prepared to 216 g. (0.2 mole)trimethylchlorosilane, 93.2 g. (0.4 mole)methylchlorohexyldichlorosilane, 69 g. (0.6 mole) methyl hydrogendichlorosilane. This mixture was slowly added to 500 g. of stirred icewater and allowed to stand for two hours. The upper silicone layer wasseparated and washed and dried as previously described to produce apolysiloxane within the scope of Formula 6, where n is 6, a is 4, and bis 6. To this silicone fluid was added suflicient chloroplatinic acidhexahydrate to provide one gram atom of platinum per 1,000 gram atoms ofsilicon-bonded hydrogen and 78.4 g. (0.7 mole) of octene-l was slowlyadded to the reac tion mixture which was maintained at a temperature of75 C. At the end of this addition reaction, the reaction mixture wasplaced under a vacuum of 10 mm. to remove unreacted octene-l and toproduce a copolymer within the scope of Formula 1 in which n is 6, R isoctyl, a is 4, and b is 6. When 100 part portions of this copolymer aremixed, respectively, with 3 parts, 5 parts, and 15 parts of tricresylphosphate, the resulting product exhibits a wear scar below 0.40 mm.under a 10 kg. load.

While the tricresyl phosphate-containing compositions of the presentinvention have been described as liquid materials useful in thelubrication of stainless steel parts and other materials in the liquidform, it should be understood that these compositions can also beemployed as lubricating greases. For example, very useful lubricatinggreases are obtained by mixing 100 parts of the silicone fluid-tricresylphosphate compositions of the present invention with from 5 to 15 partsby weight of finely divided silica to form a grease-like lubricatingcomposition which can be used in conventional fashion. When thecompositions of the present invention are employed in the manufacture ofgreases by the addition of finely divided silica or other fillers, thequestion of miscibility of the methylchloroalkylpolysiloxane of Formula2 and the methyl higher alkylpolysiloxane of Formula 3 is unimportant,since the resulting grease can be maintained without difficulty in ahomogeneous state.

While the foregoing examples have illustrated many of the embodiments ofmy invention, it should be understood that my invention relates broadlyto the use of liquid organopolysiloxane compositions containingmethylchloroalkylsiloxane units of the type described, methyl higheralkyl polysiloxane units of the type previously described and from 1 to15 percent by weight, based on the weight of siloxanes, of tricresylphosphate. The chloroalkyl groups and the higher alkyl groups, as wellas the chain length of the polysiloxanes and the ratio of the varioussiloxane units can vary within the full range previously described.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An organopolysiloxane lubricating composition comprising (A) anorganopolysiloxane having the formula:

and (B) from 1 to 15 percent by weight, based on the Weight of saidorganopolysiloxane, of tricresyl phosphate, where R is an alkyl radicalcontaining from 8 to 18 carbon atoms, inclusive, n has a value of from 2to 6, inclusive, a has an average value of at least 1, b has an averagevalue of at least about 2.9, the sum of a plus b is equal to from about4 to 40, inclusive, and the ratio of a to the sum of a: plus b is equalto form 0.1 to 0.4 inclusive.

2. A composition of claim 1 in which said organopolysiloxane is acopolymeric organopolysiloxane.

3. The composition of claim 1 in which said organopolysiloxane comprisesa blend of a methylchloroalkylpolysiloxane having the formula:

Cl n h n Zn (CHa)3SiO i swans and a methyl higher alkyl polysiloxanehaving the formula:

R (CH SiO(S iO )Si( CH l a a References Cited UNITED STATES PATENTS2,467,178 4/ 1949 Zimmer et a1. 25249.9 2,768,193 10/1956 Gilbert2S2-46.7 X 2,970,150 1/1961 Bailey 25249.6 X 3,011,987 12/1961 Walton eta1. 260448.2 X 3,053,873 9/1962 Pepe 260448.2 3,386,917 6/1968 Schiefer25249.9

DANIEL E. WYMAN, Primary Examiner W. CANNON, Assistant Examiner US. Cl.X.R.

